The sharp drop in President Carter's overall job rating may have been triggered by the Bert Lance episode but the basic reason behind it is a steady decline in the public's confidence in his ability to handle most of the key issues facing the country.

According to the latest Harris Survey of 1.536 adults nationwide, the President's score on handling the economy and foreign policy continues to fall, while his rating on "restoring confidence in government" has also declined significantly.

By a bare 47 to 46 per cent, a narrow plurality gives him positive marks on "restoring confidence in government," compared with a substantial 64-to-31 per cent majority back in July.

On "inspiring confidence personally in the White House," Carter emerges with a current 50-to-42 per cent positive standing down from 50 to 34 per cent in July and 74 to 20 per cent back in April.

In the key issue areas with which the federal government must deal, Carter's ratings are consistently negative:

On his "handling of the economy," he has sunk to a new Carter low of 66 to 26 per cent negative from the 54-to-39 per cent negative score in August.

On "keeping down the cost of living," the President is rated 76 to 19 per cent negative, an 8-point down.

On "cutting the rate of unemployment," he has a 74-to-20 per cent negative rating, 12 points lower than before.

On foreign policy, also, Carter appears to be in trouble:

On "handling of foreign policy matters," he is given negative marks of 51-to-32 per cent, a turn-around from the 43-to-40 per cent positive standing to July.

On "handling relations with Russia," he is rated 49 to 31 per cent negative, down from the 42-to-38 per cent positive rating of July.

On "handling relations with China," he receives a 44-to-31 per cent negative rating, representing a small, but noticeable decline.

On his efforts to "achieve peace in the Middle East," Carter now stands at 47 to 34 per cent negative, whereas in July he was 53 to 35 per cent positive.

On his proposed Panama Canal treaty, now stalled in the Senate, Americans give Carter a 58-to-23 per cent negative rating.

A third major area where the President appears to be in trouble is energy:

On his "handling of the energy crisis," Carter receives a 58-to-33 per cent negative rating.

His "overall energy program" received a negative rating of 57 to 33 per cent.

Finally, the public feeling about the Lance affair still remains negative:

On his "handling of the Lance case," the President is given negaitve marks of 31 to 34 per cent.

On his "appointments to high office," he gets a 54-to-35 per cent negative rating.